Catalytic composition and hydrocarbon conversion therewith



United States Patent 1 2,849,383 CATALYTIC COMPOSITION AND HYDROCARBONCONVERSION THEREWITH Alfred E. Hirschler, Springfield, and AbrahamSchneider, Overbrook Hills, Pa., assignors to Sun Oil Company,

Philadelphia, Pa., a corporation of New Jersey No Drawing. ApplicationOctober 13, 1955 Serial No. 540,350 18 Claims. (Cl. 196-52) Thisinvention relates to catalytic compositions effective in processes forconverting hydrocarbons. More particularly this invention relates to newcatalytic compositions, their preparation, and to a process forconverting relatively high molecular weight hydrocarbons to lowerinolecular weight hydrocarbons employing the new catayst.

The conversion of petroleum hydrocarbons by processes such as cracking,reforming, destructive hydrogenation, and the like, using a variety ofcatalysts and reaction conditionshas heretofore been described. Incracking processes it is generally desired to produce a good yield ofhigh octane number gasoline and it is known that operation underrelatively high temperature conditions improves the octane number of thegasoline fraction from such processes. However, such relatively hightemperatures cause an increase in the yield of normally gaseoushydrocarbons and coke, both of which are undesired products. It is alsoknown that catalytic cracking processes should be operated withpetroleum stocks having relatively low concentrations of metalliccontaminants, such as compounds of chromium, vanadium, nickel and iron,since such contaminants form a deposit, as the metal oxide, on thecatalyst and cause a decrease in the gasoline yield and an increase inthe formation of normally gaseous hydrocarbons and coke. Thus it hasbeen reported that quantities up to one percent of an oxide of a metalsuch as. chromium or vanadium deposited on a cracking catalyst cause asignificant decrease in catalytic activity, an increase in gas formationand an increase in coke deposition (McIntosh, Paper Presented before theDivision of Petroleum Chemistry of the Am. Chem. Soc, New York Meeting,September ll-17, 1954).

An object of this invention is to provide a new catalytic compositionespecially effective for cracking hydrocarbons under relatively hightemperature conditions. Another object is to provide a new catalyticcomposition effective for cracking relatively high boiling petroleumhydrocarbons containing metal compounds as impurities. A further objectis to" provide a new process for cracking petroleum hydrocarbons whereinhigh yields of gasoline of high octane number are obtained and onlyminor quantities of normally gaseous hydrocarbons and coke are formed.Other objects and their achievement in accordance with the inventionwill be apparent from the follow ing specification.

GENERAL A new catalytic composition has beendiscovered which givesimproved results in cracking relatively high molecular weight petroleumhydrocarbons to lower molecular weight hydrocarbons boiling in thegasoline range. The new catalytic composition consists essentially of acracking catalyst and an oxide of a metal from group V or VI of theperiodic table. While the cracking catalyst portion of the newcomposition may be prepared by means heretofore known, it is essentialthat certain steps in preparing the final composition of the inventionbe performed as hereinafter described. It is also essential that thequantity of metal oxide be within the limits hereinafter defined. It hasbeen found that the new catalytic composition is especially effective inconverting relaice 2 tively high boiling petroleum fractions whichcontain substantial quantities of contaminating metal compounds to highoctane gasoline in good yield, and that in the process only minorquantities of normally gaseous hydrocarbons and coke are formed. It hasbeen further found that the normally gaseous hydrocarbons which areproduced are highly unsaturated in character and hence are especiallyvaluable for use in processes such as alkylation and polymerization.

THE CATALYST The catalyst of the invention consists essentially of asiliceous cracking catalyst, such as a silica-alumina cracking catalyst,and an oxide of a metal from group V A or Vi A of the periodic table,the preparation of which includes a specific treatment as hereinafterdescribed. By siliceous cracking catalyst is meant a synthetic ornatural siliceous composition known to be effective for the cracking ofhydrocarbons. The siliceous cracking catalyst, before deposition of theoxide, should contain at least above about 50% silica (calculated as SiOAs illustrative of the cracking catalysts which can be used, syntheticsilica-alumina, silica-magnesia, si1ica-zirconia andsilica-alumina-zirconia cracking catalysts give good results. Naturalcracking catalysts such as the bentonite and kaolin clays, which mayhave been activated with an acid, give good results. The metal oxidemust be incorporated with the cracking catalyst in a quantity of atleast 2.9% by weight, and preferably the quantity deposited is in therange of from 2.9% to 11% by weight. When quantities below 2.9% of themetal oxide are used, excessive quantities of normally gaseoushydrocarbons and coke are formed and the yield of gasoline is poor. Noadvantage accrues from using a quantity of metal oxide greater than 11%,and the use of such larger quantities mayhave deleterious effects, e.g., in promoting undesired side reactions and decreasing conversion togasoline. It is preferred to deposit metal oxide on the crackingcatalyst. However, if desired, the metal oxide can be incorporated inthe composition by coprecipitation, such as by coprecipitation withsilica, with another component such as alumina, or both, in which casethe quantities of materials in the final composition must be within thestated limits.

Especially suitable for deposition on the silica-containing crackingcatalyst are the oxides of chromium, vanadium, molybdenum and tungsten.Combinations of such oxides wherein the total quantity thereof is withinthe stated limits of from 2.9% to 11% by weight can be used if desired.

Forsimplicity the composition and the process of the invention arehereinafter described in terms of chromia deposited on a silica-aluminacracking catalyst, although the scope of the invention is limited onlyas herein indicated. To illustrate the preferred catalytic compositionof the invention, from 2.9% to 11% chromia is deposited on a syntheticsilica-alumina composition containing from 50% to by weight silica andfrom 50% to 10% alumina. The final catalytic composition thus contains,in percent by weight, from about 45% to 87.5% silica, from about 9% to48.6% alumina and from about 2.8% to 10% chromia.

PREPARATION OF CATALYST The preparation of the catalyst of the inventionis important and certain steps, as hereinafter described, must beobserved in order to obtain the desired catalytic composition. Thesilica-containing cracking catalyst, however, can be prepared by meansheretofore known. For example, the silica-alumina portion of thecatalyst can be prepared by. impregnating silica with water solublesalts of aluminum, directly combining precipitated hydrated alumina andsilica, or by joint precipitation of alumina 3 and silica from aqueoussolutions of their water soluble salts and by washing, drying andheating the resulting composition. The resulting silica-aluminacomposition should have an activity index of at least 30 and preferablyfrom 40 to 50. Activity index, as used herein, is a measure of theefliciency of the catalyst for crackinghydrocarbons and is determined bya method described by Alexander, Proceedings Am. Pet. Inst. 27 (III) 51(November 1947).

After preparation of the silica-alumina cracking catalyst chromia isdeposited thereon. This is accomplished by impregnating thesilica-alumina composition with an aqueous solution or a water solublesalt of chromium, such as ammonium dichrornate, chromium chloride,chromium nitrate, or the like. The concentration of the selected salt inthe aqueous solution, and the quantity of solution used to impregnatethe catalyst, should be such that the concentration of the resultingmetal oxide is within the defined limits. After impregnation, thesilicaalumina composition is drained, if necessary, and dried preferablyat a temperature of 100 C. to 200 C. for from 1 to 20 hours, and is thencalcined at a temperature of 500 C. to 750 C. If desired, the chromiacan be ccprecipitated with the alumina, the silica, or both, in whichcase the composition is dried and calcined as described above.

It is essential to the successful preparation of the catalyticcomposition of the invention that the calcined composition be subjectedto steaming at an elevated temperature. The steaming is performed bymaintaining the catalyst in an atmosphere of about 100% steam at atemperature of from about 600 C. to 800 C. for from about .1 hour to 8hours. It is only through the use of both a relatively large quantity ofchromia and steaming the silica-alumina-chromia composition that thehighly advantageous results of the invention are obtained. It isessential that the chromia be incorporated with the silicaalumina priorto the steaming step, since steaming the silica-alumina compositionprior to the incorporation of metal oxide does not give a compositioncomparable, for cracking, to the catalyst of the invention.

The catalytic composition of the invention, and the preparation thereof,is above illustrated by a silica-'- alumina-chromia catalyst. Othercatalysts within the scope of the invention are prepared in a similarmanner, For example, a silica-containing cracking catalyst such assilica-magnesia or the like can be prepared by means known in the art,and an oxide of chromium, vanadium, molybdenum or tungsten depositedthereon as above described for chromia. In each event, however, it isessential that the cracking catalyst having the metal oxide incorporated therewith be subjected to the steaming step as described forthe silica-alumina-chromia catalyst. It is not known with certainty why,the steaming step is essential in preparing the catalyst of theinvention and it is not desired to be limited by theoreticalconsiderations, but it is believed that the steaming causes somemodification in the physical structure of the composition which givesthe highly beneficial results in accordance with the invention.

CRACKING The cracking process of the invention employing the newcatalyst compositiomas above described, is especially valuable forconverting hydrocarbons boiling above the gasoline range to gasolinehydrocarbons in good yield without the formation of substantialquantities of gaseous hydrocarbons or coke. Especially suitable chargestocks are gas oils boiling within the range of from about 200 C. toabout 600 C., such as the gas oil. fraction boiling Within the rangefrom about 207 C. to 370 C., but other gas oils boiling within otherranges within the described limits are suitable. Especially advantageousresults are obtained with charge stocks having relatively highconcentrations of metal compounds, as impurities,.which are known todeleteriously affect the cracking activity of here-- quantity of thesame or a similar metal oxide, is not poisonedeby the addition of minorquantities of such oxides during the cracking process. I

As above stated the catalytic composition of the invention givesespecially beneficial results when used for cracking under relativelyhigh temperature conditions, say at temperatures from 450 C. to 540 C.,and preferably at temperatures within the range of from about 480 C. to540 C. Such high temperatures result in a gasoline product having arelatively high octane number so that the gasoline fraction can be used,without further processing, as motor fuel vor as a component of motorfuels blended with other suitable materials. The cracking process ispreferably operated at atmospheric pressure, but superatmosphericpressure, say up to about 50 p. s. i. g. (pounds per square inch gauge),can be used with good results. Hydrogen may be added to the process ifdesired, and good results are obtained therewith. The space rate(v./v./hr.), which is the volume of hydrocarbons charged per volume ofcatalyst per hour, should be maintained within the range from 0.5 to 6in continuous operations such as in fixed bed or moving bed processes.Although such continuous processes are preferred, batch operation can beused under conditions substantially equivalent to the conditionsdescribed above.

After operation for a substantial time catalytic activity of thecatalyst may decrease due to coke deposition, but'such decrease is muchslower than is observed with processesheretofore described. When theactivity of the catalyst is decreased to an extent so that the operationtherewith is uneconomical, the catalyst can be regenerated by the usualmeans for regenerating a silicaalumina cracking catalyst, i. e. byburning coke therefrom. Such regeneration has been found tosubstantially'restore the activity of the catalyst.

EXAMPLES Example 1 A synthetic silica-alumina cracking catalystcontaining about 87% silica and about 13% alumina and having an activityindex of about 46 was impregnated with an aqueous solution of ammoniumdichromate, dried and calcined. The calcined composition was thensubjected to an atmosphere of steam at about 732 C. for 4 hours. Theresulting composition consisted essentially of about 83.5% silica, about12.5% alumina, and about 4% chromia.

A gas oil boiling from about 207 C. to about 371 C. was contacted withthe silica-alumina-chromia catalyst at a temperature of about 510 C.using a space rate of 1 and substantially atmospheric pressure. In asingle pass 51.5% of the charge was converted. For comparison, theprocedure was repeated using the silica-alumina cracking catalyst,above-described, which had been steamed also as above described, butwhich did not contain chromia. In a single pass 57.9% of the charge wasconverted. Results obtained were as follows:

t The gasoline fractions consisted of thehydrocarbons boiling above thebutanes up to about 207 C. It will be noted that, while thesilica-alumina catalyst gave a somewhat greater conversion than thesilica-aluminachromia catalyst, the latter catalyst gave a higher yieldof gasoline. Thus, the gasoline/conversion, which is the gasolineproduced divided by the conversion obtained (calculated as 100x gasolineproduced/conversion), and which shows the selectivity of the catalystfor producing gasoline, was 71.3 for the catalyst of the invention andonly 61.3 for the silica-alumina catalyst.

Example 2 A silica-alumina-chromia catalyst containing 4.4% chromia,12.4% alumina and 83.2% silica was prepared substantially as describedin Example 1, including maintaining the silica-alumina-chromiacomposition in an atmosphere of 100% steam at about 732 C. for 4 hours.This catalyst was used to crack the same gas oil used in Example 1. Inthe cracking, the temperature was maintained at about 510 C., and thespace rate at 1. Atmospheric pressure was used and the catalyst wasregenerated, by burning, after operation for 20 minute periods. Thefollowing results were obtained, the data presented being obtained overthe indicated number of catalyst regenerations, designated 'cycles inthe table:

3-8 99-104 Cycles and 56-67 and Conversion (volume percent) 55.0 54. 354. 6 Gasoline (volume percent) 34.1 35. 3 36.0 Butaues (volumepercent)... 18. 4 18. 7 20. 1 Dry gas (Weight percent) 5. 88 6. 41 4. 09Coke (weight percent). 2. 5 2. 5 2. 5 Gasoline/conversion 62.0 65. 165.9 Octane number of gasoline (ASTM method 13908-53) 97. 2 95. 5 96. 2Oleflns in CA fraction (volume percent) 57 55 74 Olefins in Ca fraction(weight percent) 78 78 80 Example 3 the conversion being 54.1 vol.percent, and the selectivity for producing gasoline (100x gasolineproduced/conversion) being 64.8. The octane number of the gasolineproduct was 96.0 (ASTM method D908-53).

Example 4 Example 1 was repeated using, as the catalyst, thesilica-alumina-chromia composition of Example 1 prior to the steamingoperation, i. e., the catalyst was identical to the catalyst of Example1 except that it was not contacted with steam prior to use. oil ofExample 1 under the same conditions as there used, coke formation wasexcessive, the actual value being 6.2 wt. percent. Also, the olefiniccontents of the C (butane) fraction and the C (propane) fraction weresmall, the values being 36.4 vol. percent and 65.8 wt. percent,respectively. The gasoline produced/conversion was only 57.0.

When other catalysts within the limits above-defined are used, and whenother relatively high boiling petroleum fractions, especially thosecontaining relatively large amounts of compounds of metals known to becatalyst poisons, are used results substantially equivalent to thoseabove-described are obtained.

The invention claimed is: I

1. Process for converting the hydrocarbons of a relatively high boilingpetroleum fraction to lower boiling hydrocarbons which comprisescontacting said high boiling hydrocarbons, at a cracking temperature offrom 450 C. to 540 C., with a catalytic composition prepared byincorporating from 2.9% by weight to 11% In cracking the gas by weightof an oxide selected from the group consisting of chromium oxide,vanadium oxide, molybdenum oxide and tungsten oxide on a syntheticsiliceous cracking catalyst and subjecting the resulting composition tocontact with steam at a temperature of from about 600 C. to 800 C. forfrom about 1 hour to 8 hours, whereby the hydrocarbons of the relativelyhigh boiling petroleum fraction are converted to lower boilinghydrocarbons.

2. Process for preparing gasoline from a relatively high boilingpetroleum fraction which comprises contacting, under cracking conditionsincluding a temperature of from 450 C. to 540 C., a petroleum fractionboiling within the range of from about 200 C. to about 500 C. with acatalytic composition prepared by depositing from 2.9% by weight to 11%by weight an oxide selected from the group consisting of chromium oxide,vanadium oxide, molybdenum oxide and tungsten oxide on a syntheticsiliceous cracking catalyst and subjecting the resulting composition tocontact with steam at a temperature of from about 600 C. to 800 C. forfrom about 1 hour to 8 hours, and separating a gasoline fraction fromthe reaction mixture.

3. Process according to claim 2 wherein the oxide selected is chromiumoxide.

4. Process according to claim oxide selected is vanadium oxide.

5. Process according to claim 2 wherein the oxide selected is molybdenumoxide.

6. Process according to claim 2 wherein the oxide selected is tungstenoxide.

7. A new catalytic composition for use in the conversion of hydrocarbonsprepared by incorporating from 2.9% by weight to 11% by weight of anoxide of a metal selected from the group consisting of chromium oxide,vanadium oxide, molybdenum oxide and tungsten oxide with a syntheticsiliceous cracking catalyst and contacting the resulting compositionwith steam at a temperature of from about 600 C. to 800 C. for fromabout 1 hour to 8 hours.

8. A new catalytic composition according to claim 7 wherein the metaloxide selected is chromium oxide.

9. A new catalytic composition according to claim 7 wherein the metaloxide selected is vanadium oxide.

10. A new catalytic composition according to claim 7 wherein the metaloxide selected is tungsten oxide.

11. A new catalytic composition according to claim 7 wherein the metaloxide selected is molybdenum oxide.

12. A new catalytic composition according to claim 7 wherein thesynthetic siliceous cracking catalyst is a synthetic silica-aluminacracking catalyst.

13. A new catalytic composition according to claim 7 wherein thesynthetic siliceous cracking catalyst is a synthetic silica-magnesiacracking catalyst.

14. A new catalytic composition according to claim 7 wherein thesynthetic siliceous cracking catalyst is a synthetic silica-zirconiacracking catalyst.

15. Process for the preparation of a catalytic composition whichcomprises depositing of 2.9% by weight to 11% by weight of a metal oxideselected from the group consisting of chromium oxide, vanadium oxide,tungsten oxide and molybdenum oxide on a synthetic siliceous crackingcatalyst, and contacting the resulting composition with steam at atemperature of from about 600 C. to 800 C. for from about 1 hour to 8hours.

16. Process according to claim 15 wherein said synthetic siliceouscracking catalyst is a synthetic silica-alumina cracking catalyst.

17. Process for the preparation of gasoline from a petroleum fractionboiling in the range of from about 200 C. to about 500 C. having metalcompounds as impurities which comprises contacting said fraction, undercracking conditions, with a catalytic composition prepared byincorporating from 2.9% by weight to 11% by weight of an oxide selectedfrom the group consisting of chromium oxide, vanadium oxide, molybdenumoxide metal 2 wherein the metal metal metal and tungsten oxide on asynthetic siliceous cracking catalyst and subjecting the resultingcomposition to contact With steam at a temperature of from about 600 C.to 800 C. for from about 1 houI to 8 hours, and separating a gasolinefraction from the reaction mixture.

18. Process for the preparation of gasoline from a petroleum fractionboiling in the range of from about 200 C. to about 500 C. having metalcompounds as impurities which comprises contacting said fraction, undercracking conditions, with a catalytic composition prepared byincorporating from 2.9% by weight to 11% by weight of an oxide selectedfrom the group consisting of chromium oxide, vanadium oxide, molybdenum0X- ide and tungsten oxide on a natural clay cracking catalyst 8 andsubjecting the resulting composition to contact with steamat atemperature of from about 600 C. to 800 C. for from about 1110111 to 8hours, and separating a gasoline fraction from the reaction mixture.

References Citedin the-file of this patent UNITED STATES PATENTS

1. PROCESS FOR CONVERTING THE HYDROCARBONS OF A RELATIVELY HIGH BOILING PETROLEUM FRACTION TO LOWER BOILING HYDROCARBONS WHICH COMPRISES CONTACTING SAID HIGH BOILING HYDROCARBONS, AT A CRACKING TEMPERATURE OF FROM 450*C. TO 540*C., WITH A CATALYTIC COMPOSITION PREPARED BY INCORPORATING FROM 2.9% BY WEIGHT TO 11% BY WEIGHT OF AN OXIDE SELECTED FROM THE GROUP CONSISTING OF CHROMIUM OXIDE, VANADIUM OXIDE, MOLYBDENUM OXIDE AND TUNGSTEN OXIDE ON A SYNTHETIC SILICEOUS CRACKING CATALYST AND SUBJECTING THE RESULTING COMPOSITION TO CONTACT WITH STEAM AT A TEMPERATURE OF FROM ABOUT 600*C. TO 800*C. FOR FROM ABOUT 1 HOUR TO 8 HOURS, WHEREBY THE HYDROCARBONS OF THE RELATIVELY HIGH BOILING PETROLEUM FRACTION ARE CONVERTED TO LOWER BOILING HYDROCARBONS. 